Summary Islet cell transplantation is an alternative therapy for the treatment of diabetes but requires the administration of immunosuppressive drugs to avoid host rejection. Immunoisolation devices such as TheraCyte device protect islet cells from the host response and thus eliminate the need for immunosuppressive drugs. However, once implanted, hypoxic conditions around and within the device result in loss of islet cell function and viability. To alleviate these conditions, the Papas lab in collaboration with TheraCyte and other industry partners developed devices that enable supplemental oxygen delivery to encapsulated cells. Monitoring oxygen supply within implanted devices is now recognized as critical, but it is limited by currently available instrumentation that is bulky, invasive, or have slow measurement times. The Lumee O2 sensor by Profusa is a flexible, wireless, injectable fluorescent sensor that provides continuous and non-invasive measurements of oxygen. The Lumee O2 sensor has been tested extensively in small and large pre-clinical models as well as in humans for up to 1 year. We propose the integration of Profusa Lumee O2 sensors into oxygen enabled TheraCyte immunoisolation devices for the non-invasive monitoring of oxygen concentrations within these devices. Specific aims for Phase I will focus on in vitro validation of oxygen measurements from Lumee O2 sensors within oxygen enabled TheraCyte devices and assess different oxygen supplementation approaches as measured by Lumee O2 sensors on device vascularization in vivo. Main outcomes of this collaborative effort will be monitoring oxygen delivery to devices to improve islet cellular function and the demonstration of Lumee O2 sensors as a new tool for oxygen monitoring within implantable cellular-based devices.